(a) Field of the Invention
The present invention relates to a switch controller, a switch control method, and a power supply using the switch controller.
(b) Description of the Related Art
A power switch controlling operation of a power supply is connected with a sense resistor for sensing a drain current flowing to the power switch.
In general, a sense voltage generated in the sense resistor and a predetermined reference voltage are compared to sense a short-circuit state of the sense resistor. That is, when the sense voltage is maintained to be lower than the reference voltage for a constant period of time, the sense resistor is determined to be short-circuited.
The reference voltage is set to sense the short-circuit state of the power switch in a switch control IC controlling switching operation of the power switch. However, an error may occur in sensing of the short-circuit state depending on an external set condition to which the switch control IC is applied, that is, an external set condition of the power supply.
For example, the external set condition includes an inductance of an inductor used in the power supply or a VIN voltage supplied to the inductor. In this case, a slope of the sense voltage becomes less steep when the inductance is large or the VIN voltage is low so that the short-circuit state cannot be accurately determined.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.